The histogram below shows the amount of time spent on a new app on mobile phones by thousand teenagers over the period of a week. The numbers on top of each bar represent its heights. You may assume that the values are spread uniformly across each interval. \".2 3.5 m m \"'3 L N 3 E L N 8 o m. '8\\ .I H I\". O O 0 20 40 60 80 100 Time per week (hours) What percentage of the teenagers spent between 20 and 40 hours using the app? Enter a number between 0 and 100 giving the percentage. (Do not enter the % Sign.)